1. Field of the Invention
The present invention relates to underwater vision devices, and more particularly, to underwater vision devices having multi-element lenses which provide neutral magnification above the surface of water and strong magnification below the surface of the water to permit a wearer to see normally both above and below the surface of the water without adjusting the device.
2. Description of the Prior Art
A variety of various types of underwater vision devices are disclosed in the prior art. U.S. Pat. No. 2,008,530 (Wick) discloses submarine glasses coupled to a spectacle-like frame and are intended to be worn by a swimmer either above or below the surface of a body of water. Each of the two optical systems of these glasses is fabricated from thin transparent celluloid and includes a sealed air chamber. These lens elements function only in the presence of water; in the air the negligible thickness of the transparent celluloid fails to have any significant refractive effect on light passing through each lens element. Because of this characteristic, the Wick submarine glasses can be worn either above or below water.
U.S. Pat. No. 2,088,262 (Grano) discloses underwater spectacles. Many of the various lens embodiments disclosed in the Grano patent are fabricated from glass, but several embodiments include an air filled chamber adjacent to a glass lens.
U.S. Pat. No. 3,040,616 (Simpson) discloses a face mask which includes an air chamber between the transparent front surface of the face mask and the face of the wearer. A complex lens system is positioned in alignment with the eye of the wearer. Each element of this lens system includes a transparent refractive material, an air cavity and a layer of water. The purpose of this invention is to permit the wearer of the device to see normally while above or below the surface of the water.
U.S. Pat. No. 3,672,750 (Hagen) discloses an underwater diving mask which includes a pair of lens systems which form an air chamber between the face mask and the eyes of the wearer. The central portion of each part of this mask which is aligned with an eye of the wearer includes a corrective spherical lens. This mask allows an underwater diver to have vision substantially comparable with that which he would have in an air environment.
The following U.S. patents disclose optical systems which utilize various types of optical mediums of varying refractive indices: U.S. Pat. Nos. 3,976,364 (Lindemann); 2,730,014 (Ivanoff); and 3,320,018 (Pepke).